CCR7+ Dendritic Cells Define a Type 17 Module in Psoriasis

Interleukin (IL)-23 is the master pathogenic cytokine in psoriasis and neutralization of IL-23 alleviates psoriasis. Psoriasis relapses after the withdrawal of IL-23 antibodies, and the persistence of IL-23-producing cells probably contributes to such recurrence. However, the cellular source of IL-23 was unclear, which hinders the development of targeted therapies focusing on modulating IL-23 expression aimed at resolving relapse. Here, we showed that IL4I1+CD200+CCR7+ dendritic cells (CCR7+ DC) dominantly produced IL-23 by concomitantly expressing the IL-23A and IL-12B subunits in human psoriatic skin. Deletion of CCR7+ DC completely abrogated IL-23 production in a mouse model of psoriasis and enforced expression of IL-23a in CCR7+ DC elicited not only {beta}T cell-driven psoriasis-like skin disease, but also arthritis. CCR7+ DC co-localized with CD161+ IL-17-producing T cells and KRT17+ keratinocytes, which were located in the outermost layers of psoriatic epidermis and strongly exhibited IL-17 downstream signatures. Based on these data, we identified CCR7+ DC as the source of IL-23 in psoriasis, which paves the way for the design of therapies focused on manipulating IL-23 production that may resolve the relapse of chronic inflammatory disorders like psoriasis. HIGHLIGHTSO_LIIL4I1+CD200+CCR7+ DC are dominant IL-23 producers in psoriasis and its mouse model. C_LIO_LIPsoriatic CCR7+ DC likely arise from cDC2. C_LIO_LICD161 marks all IL-17-producing T cells in psoriatic skin. C_LIO_LIIL-23a overexpression in CCR7+ DC elicits an {beta}T cell-driven mouse model of psoriasis and arthritis. C_LIO_LICCR7+ DC spatially define a type 17 module in psoriatic epidermis. C_LI